FCC process

ABSTRACT

The present invention is a fluidized catalytic cracking process that incorporates a zoned riser reactor. The process provides an in-situ method for feed upgrading in a riser reactor. The process assists in the removal of undesirable contaminants, such as nitrogen, from FCC feedstocks.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims benefit of U.S. provisional patentapplication serial No. 60/191,579 filed Mar. 23, 2000, serial No.60/191,530 filed Mar. 23, 2000, and serial No. 60/246,317 filed Nov. 6,2000.

BACKGROUND

[0002] The present invention relates to a fluidized catalytic crackingprocess that incorporates a zoned riser reactor.

[0003] Catalytic cracking is an established and widely used process inthe petroleum refining industry for converting relatively high boilingproducts to more valuable lower boiling products including gasoline andmiddle distillates, such as kerosene, jet fuel and heating oil. Thepre-eminent catalytic cracking process is the fluid catalytic crackingprocess (FCC) wherein a pre-heated feed contacts a hot crackingcatalyst. During the cracking reactions, coke and hydrocarbons depositon the catalyst particles, resulting in a loss of catalytic activity andselectivity. The coked catalyst particles, and associated hydrocarbonmaterial, are stripped, usually with steam, to remove as much of thehydrocarbon material as technically and economically feasible. Thestripped particles, containing non-strippable coke, pass from thestripper and to a regenerator. In the regenerator, the coked catalystparticles are regenerated by contacting them with air, or a mixture ofair and oxygen, at elevated temperatures, resulting in the combustion ofthe coke—an exothermic reaction. The coke combustion removes the cokeand heats the catalyst to the temperatures appropriate for theendothermic cracking reactions.

[0004] The process occurs in an integrated unit comprising the crackingreactor, the stripper, the regenerator, and the appropriate ancillaryequipment. The catalyst is continuously circulated from the reactor orreaction zone, to the stripper and then to the regenerator and back tothe reactor. The circulation rate is typically adjusted relative to thefeed rate of the oil to maintain a heat balanced operation in which theheat produced in the regenerator is sufficient for maintaining thecracking reaction with the circulating, regenerated catalyst being usedas the heat transfer medium.

[0005] There is a growing need to process heavier feeds containingcontaminants such as nitrogen in FCC operations. Therefore, a needexists for a process that can perform in-situ upgrading ofnitrogen-containing feeds that can effectively and efficiently minimizethe problems caused by nitrogen-containing FCC feeds.

[0006] Additionally, an increased demand for high octane, low emissionsfuels and hydrocarbons useful for olefin production has led to a desireto increase the light (C₂-C₄) olefin content is riser reactor products.Typical heavy oil, gas oil, or resid feeds for riser reactor processesgenerally contain at most small amounts of light olefins, if any.Catalytic cracking in the riser reactor produces light olefins; however,these products may be thermally cracked into undesirable products suchas catalyst coke, diolefins, and dry gas (including methane). Theseproducts may also be saturated via hydrogen transfer reactions beforethey reach the end of the riser. Both activities reduce theconcentrations of high-octane naphtha and light olefins.

SUMMARY

[0007] One embodiment of the present invention is a catalytic crackingprocess comprising (a) contacting a first portion of catalyst with asecondary feed in a first upstream zone wherein the secondary feed has aboiling range between about 25° C. and about 250° C.; (b) in a firstprimary feed conversion zone, contacting a primary feed comprisingnitrogen contaminants with the first portion of catalyst passed from thefirst upstream zone, wherein the temperature in the first primary feedconversion zone is greater than about 450° C., thereby vaporizing asubstantial portion of the primary feed; (c) passing the effluent fromthe first primary feed conversion zone to a secondary primary feedconversion zone and contacting the effluent from the first primary feedconversion zone with a second portion of catalyst under catalyticcracking conditions.

[0008] Another embodiment comprises a catalytic cracking processcomprising (a) passing a first portion of regenerated catalyst to a FCCreactor configured to have a plurality of zones; (b) in a first upstreamzone, contacting the first portion of regenerated catalyst with asecondary FCC feed, the secondary feed comprising steam and hydrocarbonsboiling in the range of about 25° C. to about 250° C. wherein theresidence time of the secondary feed in the first upstream zone is lessthan about 1.5 seconds; (c) in a first primary feed conversion zonedownstream from the first upstream zone, contacting the effluent fromthe first upstream zone with a primary FCC feed, wherein the effluent ofthe first upstream zone has sufficient enthalpy to vaporize at least 50wt % of the FCC primary feed, the primary FCC feed comprisinghydrocarbons boiling in the range of between about 250° C. and about575° C., wherein the residence time within the first primary feedconversion zone is between about 0.2 and about 2 seconds and thecatalyst to oil weight ratio is between about 2:1 and about 5:1; (d)contacting a second portion of regenerated catalyst with a secondary FCCfeed, the second portion of regenerated catalyst comprising a catalyticcracking catalyst, the secondary feed comprising steam and hydrocarbonsboiling in the range of about 25° C. to about 250° C. and then passingthe second portion of regenerated catalyst and partially convertedsecondary FCC feed to a second primary feed conversion zone positioneddownstream from the first primary feed conversion zone; and, (e) in thesecond primary feed conversion zone, contacting the effluent of thefirst primary feed conversion zone with the second portion ofregenerated catalyst wherein the residence time within the secondprimary feed conversion zone is less than about 10 seconds.

[0009] Another embodiment of the present invention comprises a catalyticcracking process comprising (a) passing a first portion of regeneratedcatalyst to a FCC reactor configured to have a plurality of zones; (b)in a first upstream zone, contacting the first portion of regeneratedcatalyst with a secondary FCC feed, the secondary feed comprising steamand hydrocarbons boiling in the range of about 25° C. to about 250° C.wherein the residence time of the secondary feed in the first upstreamzone is less than about 1.5 seconds; (c) in a first primary feedconversion zone downstream from the first upstream zone, contacting theeffluent from the first upstream zone with a primary FCC feed, whereinthe effluent of the first upstream zone has sufficient enthalpy tovaporize at least 50 wt % of the FCC primary feed, the primary FCC feedcomprising hydrocarbons boiling in the range of between about 250° C.and about 575° C., wherein the residence time within the firstconversion zone is between about 0.2 and about 2 seconds and thecatalyst to oil weight ratio is between about 2:1 and about 5:1; (d) ina second primary feed conversion zone downstream from the first primaryfeed conversion zone, contacting the effluent of the first primary feedconversion zone with a second portion of regenerated catalyst passedinto the second conversion zone, the regenerated catalyst passed intothe second conversion zone comprising a catalytic cracking catalystwherein the residence time within the second primary feed conversionzone is less than about 10 seconds; and (e) in a third primary feedconversion zone downstream from the second primary feed conversion zone,contacting the effluent of the second primary feed conversion zone witha third portion of regenerated catalyst passed into the third conversionzone, the regenerated catalyst comprising a catalytic cracking catalyst,wherein the residence time in the third primary feed conversion zone isbetween about 0.2 and 1 second.

[0010] Another embodiment is a catalytic cracking process comprising (a)passing a first portion of regenerated catalyst to a FCC reactorconfigured to have a plurality of zones; (b) in a first upstream zone,contacting the first portion of regenerated catalyst with a secondaryFCC feed, the secondary feed comprising steam and hydrocarbons boilingin the range of about 25° C. to about 250° C. wherein the residence timeof the secondary feed in the first upstream zone is less than about 1.5seconds; (c) in a first primary feed conversion zone downstream from thefirst upstream zone, contacting the effluent from the first upstreamzone with a primary FCC feed, wherein the effluent of the first upstreamzone has sufficient enthalpy to vaporize at least 50 wt % of the FCCprimary feed, the primary FCC feed comprising hydrocarbons boiling inthe range of between about 250° C. and about 575° C., wherein theresidence time within the first conversion zone is between about 0.2 andabout 2 seconds and the catalyst to oil weight ratio is between about2:1 and about 5:1; (d) contacting a second portion of regeneratedcatalyst with a secondary FCC feed, the second portion of regeneratedcatalyst comprising a catalytic cracking catalyst, the secondary feedcomprising steam and hydrocarbons boiling in the range of about 25° C.to about 250° C. and then passing the second portion of regeneratedcatalyst and partially converted secondary FCC feed to a second primaryfeed conversion zone; (e) in the second primary feed conversion zone,positioned downstream from the first primary feed conversion zone,contacting the effluent of the first primary feed conversion zone withthe second portion of regenerated catalyst wherein the residence timewithin the second primary feed conversion zone is less than about 10seconds; (f) contacting a third portion of regenerated catalyst with asecondary FCC feed, the third portion of regenerated catalyst comprisinga catalytic cracking catalyst, the secondary feed comprising steam andhydrocarbons boiling in the range of about 25° C. to about 250° C. andthen passing the third portion of regenerated catalyst and partiallyconverted secondary FCC feed to a third primary feed conversion zone;and, (g) in the third primary feed conversion zone downstream from thesecond primary feed conversion zone, contacting the effluent of thesecond primary feed conversion zone with the third portion ofregenerated catalyst wherein the residence time in the third primaryfeed conversion zone is between about 0.2 and about 1 second.

[0011] Another embodiment is a catalytic cracking process comprising (a)passing a first portion of catalyst to a FCC reactor configured to havea plurality of zones, the first portion of catalyst comprising aregenerated catalyst and an at least partially coked catalyst; (b) in afirst primary feed conversion zone, contacting the first portion ofcatalyst with a primary FCC feed, wherein the first portion of catalysthas sufficient enthalpy to vaporize at least 50 wt % of the FCC primaryfeed, the primary FCC feed comprising hydrocarbons boiling in the rangeof between about 250° C. and about 575° C., wherein the residence timewithin the first primary feed conversion zone is between about 0.2 andabout 2 seconds and the catalyst to oil weight ratio is between about2:1 and about 5:1; (c) in a second primary feed conversion zone,positioned downstream from the first primary feed conversion zone,contacting the effluent of the first primary feed conversion zone with asecond portion of catalyst wherein the residence time within the secondprimary feed conversion zone is less than about 10 seconds; and, (d) ina third primary feed conversion zone downstream from the second primaryfeed conversion zone, contacting the effluent of the second primary feedconversion zone with a third portion of catalyst wherein the residencetime in the third primary feed conversion zone is between about 0.2 andabout 1 seconds.

[0012] Another embodiment is catalytic cracking process comprising (a)passing a first portion of regenerated catalyst to a FCC reactorconfigured to have a plurality of zones; (b) in a first upstream zone,contacting the first portion of regenerated catalyst with a secondaryFCC feed, the secondary feed comprising steam and hydrocarbons boilingin the range of about 25° C. to about 250° C. wherein the residence timeof the secondary feed in the first upstream zone is less than about 1.5seconds; and, (c) in a first primary feed conversion zone downstreamfrom the first upstream zone, contacting the effluent from the firstupstream zone with a primary FCC feed, wherein the effluent of the firstupstream zone has sufficient enthalpy to vaporize at least 80 wt % ofthe FCC primary feed, the primary FCC feed comprising hydrocarbonsboiling in the range of between about 250° C. and about 575° C.

[0013] Another embodiment is a process comprising: (a) passing a vacuumresid having boiling range greater than about 565° C. (about 1050° F.)to a resid processing unit; (b) separating a light resid fraction havingboiling range between about 565° C. and about 650° C. (about 1200° F.)from the vacuum resid; (c) combining the light resid fraction with a FCCfeed; (d) passing the combined FCC feed to a FCC unit configured to havea plurality of reaction zones; (e) in the FCC unit: (i) contacting afirst portion of catalyst with a secondary feed in a first upstreamzone, the secondary feed having a boiling range between about 25° C. andabout 250° C.; (ii) in a first primary feed conversion zone, contactingthe combined feed comprising nitrogen contaminants with the firstportion of catalyst passed from the first upstream zone, wherein thetemperature in the first primary feed conversion zone is greater thanabout 450° C., thereby vaporizing a substantial portion of the combinedfeed; and, (iii) passing the effluent from the first primary feedconversion zone to a secondary primary feed conversion zone andcontacting the effluent from the first primary feed conversion zone witha second portion of catalyst under catalytic cracking conditions.

[0014] Another embodiment is a process comprising: (a) passing aatmospheric pipe still bottoms stream to a vacuum pipe still; (b)separating a vacuum gas oil having a boiling range between about 340° C.and about 565° C. from the bottoms stream, the remainder comprising avacuum resid fraction; (c) passing at least a portion of the vacuumresid fraction to a short-path distillation unit; (d) in the short-pathdistillation unit, separating a lighter resid fraction having a boilingrange between about 565° C. and about 650° C. (about 1200° F.); (e)combining the lighter resid fraction with the vacuum gas oil to form aFCC feed; (f) passing the FCC feed to a FCC unit configured to have aplurality of reaction zones; and, (e) in the FCC unit: (i) contacting afirst portion of catalyst with a secondary feed in a first upstreamzone, the secondary feed having a boiling range between about 25° C. andabout 250° C.; (ii) in a first primary feed conversion zone, contactingthe FCC feed comprising nitrogen contaminants with the first portion ofcatalyst passed from the first upstream zone, wherein the temperature inthe first primary feed conversion zone is greater than about 450° C.,thereby vaporizing a substantial portion of the FCC feed; and, (iii)passing the effluent from the first primary feed conversion zone to asecondary primary feed conversion zone and contacting the effluent fromthe first primary feed conversion zone with a second portion of catalystunder catalytic cracking conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 illustrates an embodiment of a riser used with the presentprocess wherein the riser has three zones.

[0016]FIG. 2 illustrates an embodiment of a riser used with the presentprocess wherein the riser has four zones.

[0017]FIG. 3 illustrates another embodiment of a riser used with thepresent process wherein the riser has four zones.

[0018]FIG. 4 illustrates an embodiment of a riser used with the presentprocess wherein the riser has five zones.

DETAILED DESCRIPTION

[0019] Suitable FCC feeds for the process of the present inventioninclude hydrocarbon oils boiling in the range of about 430° F. to about1050° F. (220° C.-565° C.), such as gas oil, heavy hydrocarbon oilscomprising materials boiling above 1050° F. (565° C.), heavy and reducedpetroleum crude oil, petroleum atmospheric distillation bottoms,petroleum vacuum distillation bottoms, pitch, asphalt, bitumen, otherheavy hydrocarbon residues, tar sand oils, shale oil, liquid productsderived from coal liquefaction processes, and mixtures thereof. Smallamounts (less than about 15 wt. %) of higher boiling fractions such asvacuum resids may be added to the feedstocks.

[0020] The invention is useful for riser reactor processes such asfluidized catalytic cracking (FCC) processes. The FCC process preferablyoccurs in an integrated unit comprising a riser reactor 500, a stripper,a regenerator, and appropriate ancillary equipment. The crackingcatalyst continuously circulates from the reactor 500 to the stripper tothe regenerator and back to the reactor 500.

[0021] In a conventional FCC process, a pre-heated feed contacts theregenerated cracking catalyst that cracks the heavier hydrocarboncomponents into more valuable products having a lower boiling point.During the cracking reactions, coke and hydrocarbons deposit on thecatalyst particles, resulting in a loss of catalytic activity. Thecatalyst particles then separate from the vapor products in a solid/gasseparator, such as a cyclone. The coked catalyst particles, and anyassociated hydrocarbon material, are stripped, usually with steam, toremove the strippable (volatile) components. The stripped componentspass with the cracked products to a fractionator.

[0022] The stripped particles, containing non-strippable coke, pass fromthe stripper to the regenerator where the coked catalyst particles areregenerated by contacting air, or a mixture of air and oxygen, atelevated temperatures. Suitable regeneration conditions include atemperature from about 1100 to about 1500° F. (593° C.-816° C.), and apressure ranging from about 0 to about 150 psig (101-1136 kPa).Regeneration burns at least a portion of the coke off the catalyst andheats the catalyst to the temperatures necessary for the endothermiccracking conditions in the reactor 500.

[0023] The catalytic cracking catalyst used in the present process maybe any conventional FCC catalyst. Suitable catalysts include (a)amorphous solid acids, such as alumina, silica-alumina, silica-magnesia,silica-zirconia, silica-thoria, silica-beryllia, silica-titania, and thelike, and (b) zeolite catalysts containing faujasite. Silica-aluminamaterials suitable for use in the present invention are amorphousmaterials containing about 10 to 40 wt. % alumina. Other promoters mayor may not be added.

[0024] The catalyst may also comprise zeolite materials that areiso-structural to zeolite Y, including the ion-exchanged forms such asthe rare-earth hydrogen and ultra stable (USY) form. The particle sizeof the zeolite may range from about 0.1 to 10 microns, preferably fromabout 0.3 to 3 microns. The zeolite is mixed with a suitable porousmatrix material when used as a catalyst for fluid catalytic cracking.The catalyst may contain at least one crystalline aluminosilicate, alsoreferred to herein as a large-pore zeolite, having an average porediameter greater than about 0.7 nanometers (nm). The pore diameter, alsosometimes referred to as effective pore diameter, is measured usingstandard adsorption techniques and hydrocarbons of known minimum kineticdiameters. See Breck, Zeolite Molecular Sieves, 1974 and Anderson etal., J. Catalysis 58, 114 (1979), both of which are incorporated hereinby reference. Zeolites useful in the second catalytic cracking catalystare described in the “Atlas of Zeolite Structure Types”, eds. W. H.Meier and D. H. Olson, Butterworth-Heineman, Third Edition, 1992, whichis hereby incorporated by reference.

[0025] The large-pore zeolites may include “crystalline admixtures”which are thought to be the result of faults occurring within thecrystal or crystalline area during the synthesis of the zeolites. Thecrystalline admixtures are themselves medium-pore-size, shape-selectivezeolites and are not to be confused with physical admixtures of zeolitesin which distinct crystals of crystallites of different zeolites arephysically present in the same catalyst composite or hydrothermalreaction mixtures.

[0026] The catalytic cracking catalyst particles may contain metals suchas platinum, promoter species such as phosphorous-containing species,clay filler, and species for imparting additional catalyticfunctionality such as bottoms cracking and metals passivation. Such anadditional catalytic functionality may be provided, for example, byaluminum-containing species. In addition, individual catalyst particlesmay contain large-pore zeolite, amorphous species, other componentsdescribed herein, and mixtures thereof.

[0027] Non-limiting porous matrix materials that may be used includealumina, silica-alumina, silica-magnesia, silica-zirconia,silica-thoria, silica-beryllia, silica-titania, and ternarycompositions, such as silica-alumina-thoria, silica-alumina-zirconia,magnesia, and silica-magnesia-zirconia. The matrix may also be in theform of a cogel. The matrix itself may possess acidic catalyticproperties and may be an amorphous material. The inorganic oxide matrixcomponent binds the particle components together so that the catalystparticle product is hard enough to survive inter-particle and reactorwall collisions. The inorganic oxide matrix may be made according toconventional processes from an inorganic oxide sol or gel that is driedto bind the catalyst particle components together. Preferably, theinorganic oxide matrix is not catalytically active and comprises oxidesof silicon and aluminum. Preferably, separate alumina phases may beincorporated into the inorganic oxide matrix. Species of aluminumoxyhydroxides, boehmite, diaspore, and transitional aluminas such asα-alumina, β-alumina, γ-alumina, δ-alumina, ε-alumina, κ-alumina, andρ-alumina can be employed. The alumina species may be an aluminumtrihydroxide such as gibbsite, bayerite, nordstrandite, or doyelite. Thematrix material may also contain phosphorous or aluminum phosphate.

[0028] The catalyst of the present invention may also comprise one ormore known nitrogen scavenger catalysts, including, but not limited to,amorphous aluminosilicates, acid clays, hydrogen or ammonium exchangedmordenite, clinoptilolite, chabazite, erionite, mineral acids or mineralacid precursors supported on a previously described matrix material, andCatapal alumina. Acid clays include kaolin, halloysite, sepiolite, andvermiculite. Mineral acids may include phosphoric acid, sulfuric acid,and boric acid. Mineral acid precursor refers to a compound that willform a mineral acid when subjected to FCC conditions.

[0029] Preferably, the nitrogen scavenger has a relatively low catalyticactivity. If desired, in one embodiment, the nitrogen scavenger catalystis less dense than the conventional FCC catalyst previously described.The difference in density provides at least two advantages. First, thelower density of the nitrogen scavenger catalyst decreases the lift gas300 (steam) requirements for passing the catalyst up the riser. Second,by using a less dense nitrogen scavenger catalyst, selective catalystseparation may occur in the regenerator. Because the nitrogen scavengeris less dense, the fluidization of the regenerator bed causes: (a) thenitrogen scavenger to migrate to the top of the regenerator catalystbed; and, (b) the conventional catalyst to migrate to the bottom of theregenerator catalyst bed. Accordingly, the nitrogen scavenger may bewithdrawn at or near the top of the regenerator catalyst bed, and theconventional FCC catalyst may be withdrawn at or near the bottom of theregenerator catalyst bed. Of course, other suitable separationtechniques may be employed if catalyst separation is desired.

[0030] When a nitrogen scavenger catalyst is incorporated into thepresent process, the nitrogen scavenger comprises all or a portion ofthe regenerated catalyst 400 passed into zone I if separation techniquesare used. If no separation is used, the catalyst 400 passed to theupstream end of the reactor 500 comprises both the nitrogen scavengerand the conventional FCC catalyst.

[0031] Viewing FIG. 1, the present process incorporates a riser reactor500 having one or more, preferably three zones I, II, III—although insome embodiments, the riser reactor may be configured to have four orfive zones (zones IV and V). A first portion of the catalyst 400 fromthe regenerator (not shown) passes through a standpipe and enters thebase of the riser reactor 500 by any conventional means. For example,FIG. 1 illustrates one configuration employing a J-bend where a lift gas300, preferably steam, provides some of the lift necessary to flow thecatalyst 400 up through reactor 500.

[0032] In an embodiment of the present process incorporating a riserreactor 500 with three zones—a first zone I, a second zone II downstreamfrom zone I, and a third zone III downstream from zone II—a primary feed100 passes into zone II and a secondary feed 200 passes upstream intozone I, also referred to herein as the first upstream zone.

[0033] The secondary feed 200 preferably comprises hydrocarbons havingboiling point between 25° C. and 250° C. and includes, but is notlimited to, light cat naphtha (LCN), heavy cat naphtha, light cycle oil,virgin naphtha, hydrocracked naphtha, coker naphtha, and/or combinationsthereof. Secondary feed 200 preferably comprises LCN and additionalsteam. Secondary feed 200 passes into zone I of the riser reactor 500.LCN is a hydrocarbon stream having a final boiling point less than about140° C. (300° F.) and comprises olefins in the C₅-C₉ range, single ringaromatics (C₆-C₉) and paraffins in the C₅-C₉ range. LCN passes into zoneI together with about 2 to about 50 wt. % steam based on the totalweight of LCN. Zone I is configured so that the LCN and steam passedinto zone I have a vapor residence time less than about 1.5 sec.,preferably less than about 1.0 sec. and more preferably between about0.1 and about 1 sec. Cat/oil ratios range between about 30:1 and about150:1 (wt.:wt.), pressures range between about 100 and about 400 kPa,and catalyst temperatures range from about 620° C. to about 775° C.

[0034] The injection of steam and LCN into zone I results in (a)increased C₃ and C₄ olefin yields by cracking C₅-C₉ olefins in the LCN,and (b) a reduced volume of naphtha that has an increased octane value.At least about 5 wt. % of the C₅-C₉ olefins are converted to C₃ and C₄olefins. While not wanting to be bound by any theory, applicants believethat adjusting the LCN feed rate into zone I regulates the amount ofcoke formed on the zeolite component of the catalyst. Regulating theamount of coke on the zeolite enables a degree of control over theamount of catalytic conversion that occurs in the subsequent, downstreamzone(s). Moreover, regulating the secondary feed 200 rate into zone Iregulates the temperature and consequently, the conversion andadsorption of nitrogen-containing species in the subsequent downstreamzone(s).

[0035] The effluent from zone I flows to a second zone II, also referredto herein as the first primary feed conversion zone. In zone II, aprimary FCC feed 100 passes into the riser reactor 500 and contacts theup-flowing catalyst 400. Reaction conditions in zone II include initialcatalyst temperature of from about 570° C. to about 725° C. at pressuresof from about 100 to about 400 kPa and cat:oil ratios of about 2:1 toabout 5:1 (wt.:wt.). Zone II is configured so that vapor residence timesrange from about 0.2 to about 2 seconds, preferably from about 0.2 toabout 1 second, and more preferably from about 0.2 to about 0.5 seconds.Average temperatures in zone II largely depend on the boiling range ofthe primary FCC feed 100. Typically, the average temperature ranges fromgreater than about 450° C. to about 550° C., and preferably from about480° C. to about 500° C. In one embodiment using a conventional heavyoil feed having a gravity of 20° API and a Watson characterizationfactor (“K_(w)”) of about 11.6, the catalyst exiting zone I has atemperature of at least 480° C., and preferably ranging from about 480°C. to about 500° C.

[0036] The effluent from zone I should have sufficient enthalpy tovaporize at least about 50 wt. % of the primary FCC feed 100, morepreferably at least 80 wt. %, and more preferably at least about 90 wt.%, based on the total weight of the primary FCC feed 100. While notwishing to be bound by any theory or model, it is believed that when atleast 80 wt. % of the primary FCC feed 100 is vaporized in zone II, asubstantial portion of the nitrogen-containing impurities in the primaryFCC feed 100 are irreversibly adsorbed onto the catalyst and convertedto coke, thus removing at least a portion of the impurities from theprimary FCC feed 100. This effect should increase as the molecularweight and basicity of the nitrogen-containing species increases. Thebulk of the nitrogen removed leaves the reactor in the form of coke oncatalyst, while a smaller fraction may yield ammonia.

[0037] Controlling the enthalpy of the effluent from zone I so that atleast 80 wt. % of the primary FCC feed 100 is vaporized but so thatthere is not significant primary FCC conversion, leads to a relativelylow catalyst to primary FCC feed ratio and a lower average temperaturein zone II. Applicants believe that the lower average temperature inzone II favors adsorption by the catalyst of undesirablenitrogen-containing species in the primary FCC feed 100. Additionally,lower average temperatures result in reduced thermal cracking andconsequently, improved selectivity to naphtha and light olefins.

[0038] Effluent from zone II may be further converted (catalyticallycracked) in subsequent reaction zones in the riser 500 and passed to thecyclones and stripper as previously described.

[0039] In one embodiment of the present invention, the riser reactor 500is configured to have a third zone III between zone II and riser reactoroutlet. The conditions in zone III may be regulated to take advantage ofthe in-situ feed upgrading process previously described.

[0040] In zone III, also referred to herein as the second primary feedconversion zone, fresh regenerated catalyst 401, preferably comprising aconventional FCC catalyst, passes into the riser reactor 500 through oneor more ports 250 in zone III to contact the upgraded primary FCC feedeffluent from zone II, which includes catalyst 400. Catalyst 401 maypass into the reactor 500 in any conventional manner. Contacting theupgraded FCC feed with fresh regenerated catalyst 401 leads tosubstantially less coke and nitrogen deposition on the regeneratedcatalyst 401 passed into zone III, which leads to an effective increasein catalyst activity.

[0041] Catalyst to oil ratio in zone III may be adjusted by regulatingthe feed rates of the catalyst(s) passed into the first zone I and thirdzone III. Preferably, the amount of regenerated catalyst passed 401 intozone III (R₃) exceeds the amount of catalyst 400 passed into zone I(R₁). More preferably, the ratio of R₃ to R₁ ranges from about 1:2 toabout 2:1.

[0042] Conditions in zone III are similar to those in a conventional FCCoperation and include (i) temperatures from about 500° C. to about 650°C., preferably from about 500° C. to about 600° C.; (ii) hydrocarbonpartial pressures from about 10 to about 40 psia (70-280 kPa),preferably from about 20 to about 35 psia (140-245 kPa); and, (iii) acatalyst to oil (wt:wt) ratio from about 3:1 to about 12:1, preferablyfrom about 4:1 to about 10:1.

[0043] The increased availability of strong catalyst acid sites in zoneIII enables the attainment of the required feed conversion at relativelyshort contact (residence) times of less than ten seconds, morepreferably between about 2 and about 5 seconds, and even more preferablyless than 2 seconds. As used herein, contact time and residence time aresynonymous and are used to designate the average residence time of thesolids (catalyst) passing through a particular zone. Applicants believethat contacting freshly regenerated catalyst in zone III with upgradedfeed passing from zone II leads to substantially less coke and nitrogendeposition on the catalyst. In turn, this results in an effectiveincrease in catalyst conversion activity. Coke yields from zone IIIdecrease due to reduced hydrogen transfer and enhanced primary cracking,thus allowing the option of constant coke operation via increased zoneIII cat to oil ratios.

[0044]FIG. 2 illustrates another embodiment of the present invention.Riser reactor 500 is configured to have a fourth zone IV, also referredto herein as a second upstream zone, positioned upstream from port(s)250 (or port(s) 350 as described below). In zone IV, another stream ofsecondary feed 200, preferably LCN, contacts catalyst stream 401 beforecatalyst stream 401 passes through port(s) 250. The additional LCNinjection occurs as previously described for zone I (and may includesteam co-injection). Incorporating zone IV helps quench the temperatureof the subsequent zones, minimizes thermal cracking and aromaticsformation, and generates additional light olefins by conventionalcracking. Zone IV also provides the option of increasing the cat to oilratio without unwanted increases in the subsequent reaction zonetemperatures. Operating conditions for the optional zone IV lie withinthose previously described for zone I.

[0045] Viewing FIG. 3, in another embodiment, the riser reactor 500employs a fifth zone, zone V, also referred to herein as the thirdprimary feed conversion zone. In an embodiment including zone V, whichmay or may not include zone IV, at least one additional regeneratedcatalyst inlet port(s) 350 are positioned downstream from zone III and aportion of regenerated catalyst 402 is directed through port(s) 350,although catalyst 402 may pass into zone V in any conventional manner.Port(s) 350 are configured in the same manner as described for port(s)250, but port(s) 350 are positioned downstream from port(s) 250 so thatthe contact (residence) time of the catalyst to oil between theinjection ports is between about 0.2 and about 1 second, preferablyabout 0.5 seconds. This configuration provides an additional stage offeed pretreatment. The catalyst-to-oil ratio (wt:wt) in zone V isbetween about 3:1 and about 12:1, and the temperature within zone V isbetween about 500° C. and about 650° C.

[0046] Zone V may be used in conjunction with an embodimentincorporating zones I-IV (see FIG. 4), or with an embodiment thatincorporates only zones I-III (see FIG. 3). Regenerated catalyst 402passing into zone V may also contact a secondary feed stream 200 toprovide additional advantages as already set forth for zones I and IV.The secondary feed 200 may be contacted with a single catalyst streamthat is thereafter separated into catalyst streams 401, 402, or thesecondary feed 200 may be contacted with the catalyst streams 401, 402separately. In some embodiments, the combined residence time withinzones III and V is less than about 4 seconds.

[0047] In some embodiments, the weight ratio of catalyst stream 401 tocatalyst stream 402 ranges between about 1:2 and about 1:1, and theweight ratio of catalyst stream 400 to the combined weight of catalyststreams 401 and 402 is between 1:1 and 1:2.

[0048] Coked catalyst particles and cracked hydrocarbon products exitthe riser reactor 500 and pass the cyclones where the cracked productsseparate from coked catalyst particles. Coked catalyst particles fromthe cyclones pass to a stripping zone. The stripper removes and recoversthe strippable hydrocarbons from coked catalyst particles. Strippedhydrocarbons pass with cracked hydrocarbon products for furtherprocessing. After the coked catalyst is stripped, it passes to theregenerator and eventually back to the riser reactor 500.

[0049] In other embodiments not shown in the Figures, it may bedesirable to eliminate the step of pre-contacting one or more of thecatalyst streams with a secondary feed 200. In such embodiments, thecatalyst streams flowing to the reactor 500 would comprise an at leastpartially coked catalyst, preferably having a coke content of greaterthan 0.1 wt % based upon the total weight of the catalyst charge. Insome embodiments, the catalyst would also comprise fully regeneratedcatalysts. For instance, in one embodiment, at least partially cokedcatalyst from the stripper may pass into the base of the riser reactor500 alone or in combination with regenerated catalyst 400. In anotherembodiment, at least partially coked catalyst may pass into any of thezones discussed herein in place of or in combination with catalyst thatto be pre-coked with a secondary feed 200, although applicants preferpre-coking with secondary feed 200.

[0050] In yet another embodiment, a two-stage catalyst regenerator maybe employed, and the catalyst 400 passed to the base of the riser maycomprise a first portion of substantially regenerated catalyst passedfrom one stage of the regenerator and a second portion of only partiallyregenerated and at least partially coked catalyst that passed fromanother stage of the regenerator. Applicants believe that the use of thepartially coked catalyst provides benefits similar to that found byusing catalyst pre-coked by contact with LCN or other secondary feed200.

[0051] In another embodiment of the present invention, the embodimentsof the multi-zone riser may be used in conjunction with a residupgrading unit or process, such as short-path distillation. In anembodiment employing short path distillation, high vacuum evaporation ofvolatile species from a thin liquid film spread on a heated surface isused. Evolved vapor is rapidly condensed on a closely adjacent cooledsurface. Wiper blades on the heated and cooled surfaces operatecontinuously to facilitate heat and mass transport. Typically, two ormore stages are employed. The overhead vapor is routed through anentrainment separator to minimize carryover of heavier components.Holdup is minimal and the short residence time acts to prevent thermalcracking of the overhead and bottoms streams. Short path distillation isalso described in U.S. Pat. Nos. 5,415,764 and 4,925,558, which areincorporated herein by reference to the extent they do not conflict withthe present disclosure. Short path distillation offers the potential toboost the 1050/1200° F. (565/650° C.) fraction of vacuum resid to theFCC without incurring the typical debits for high feed metals as well asrejecting the highest Conradson carbon 1200° F.+ (650° C.+) fraction.

[0052] Combining the short path distillation or other suitable processto capture a 1050/1200° F. (565/650° C.) fraction of vacuum reside withthe multi-zone FCC riser results in a synergy to capture additionaladvantage from the lower coke selectivity of the multi-zone process. Aparticular benefit from the multi-zone riser is improved coke/bottomsselectivity, which can be exploited by increasing the final boilingpoint of the primary feed to the riser. Vacuum pipe still bottoms havean initial boiling point >1050° F. (°565° C.), and small increments ofthat stream elevate nickel and vanadium concentrations in the primaryfeed, resulting in higher coke and dry gas yields. The nickel andvanadium content of the primary feed is comparable to that of typicalgas oil FCC feeds because the lighter vacuum resid fraction is typicallylow in metals. The nitrogen content and Conradson carbon content aregreater than typical gas oil FCC feeds but well suited for themulti-zone FCC riser. The multi-zone riser can tolerate increasednitrogen concentrations, but the metals contamination debits remain.Short-path distillation of vacuum pipe still bottoms and blending the1050/1200° F. (565/650° C.) fraction from the short-path distillationunit with the primary feed permits processing of the lower boilingfraction of the vacuum resid.

[0053] In a particular embodiment, a bottoms stream from an atmosphericpipe still is passed to a vacuum pipe still where a gas oil streamboiling in the about 650/1050° F. (about 340/565° C.) range is derivedfrom a vacuum pipe still (distillation column). A vacuum resid fractionboiling above 1050° F. (565° C.) passes from the vacuum pipe still to ashort-path distillation unit such as the VRSD process offered by BussAG, or other suitable resid unit. Overhead streams, referred to hereinas a lighter resid stream, having a boiling range of 1050/1200° F.(565/650° C.) taken from the resid unit are then combined with the650/1050° F. (340/565° C.) gas oil fraction obtained from the vacuumpipe still (or other suitable FCC feed stream) and may be preheated forinjection into the multi-zone riser as the primary FCC feed. Othersuitable process(es), such as solvent deasphalting, may also be used toobtain a lower final boiling point cut of lighter vacuum resid.

[0054] Boiling ranges of various streams are measured by conventionalmethods, preferably ASTM distillation.

EXAMPLES 1-3

[0055] Examples 1-3 illustrate the nitrogen removal capabilities of thepresent invention. Examples 1-3 were conducted using a conventional FCCcatalyst and a vacuum gas oil feed containing about 925 wppm totalnitrogen. The catalyst was not lightly coked by cracking a secondarylight feed. Results are therefore deemed conservative, in the sense thatlightly coked catalyst would have been expected to further suppressconversion, without adversely affecting nitrogen removal efficiency.

[0056] Example 1 represents a base case at typical cat to oil ratio andreactor temperature. Operation at these conditions results in relativelyhigh (430° F.−/221° C.−) conversion of 80 wt. %. The nitrogen removalfrom the collected liquid product was 83.3 wt. %.

[0057] Example 2 shows that reducing reactor temperature to about 944°F. (507° C.) and using a cat to oil of 3.15 (conditions that are withinthe range of operation of the zone II of the present invention) loweredconversion to 50.6 wt. %. However, a large percentage (62.1 wt. %) ofthe total feed nitrogen was removed. This is about 75% of the amount ofnitrogen removed in Example 1, but only 41% of the catalyst was used.

[0058] Example 3 data was obtained by reducing contact time to 0.33seconds, which is close to the lower end of the preferred contact timesof the present invention for the conversion zone(s). Conditionsotherwise were roughly comparable to those in Example 1. Lower contacttime significantly reduced conversion to 65.5 wt. %, but nitrogen wasstill high at 71.7 wt. %. Table 1 illustrates the results from Examples1-3. TABLE 1 Total N Contact Reactor Wt. % Removal, Time, Temp. Cat toOil (430° F.−) wt. % of Feed Example sec. ° C. Ratio Conversion N 1 1.8541 7.73 80.0 83.3 2 2.0 507 3.15 50.6 62.1 3  0.33 541 7.02 65.6 71.7

EXAMPLES 4-5

[0059] Examples 4-5 were conducted with a conventional FCC catalyst anda vacuum gas oil containing about 1900 wppm total nitrogen. Reactortemperature was 557° C. in both cases.

[0060] Example 4 represents base case FCC operation with a captive fluidbed employing a typical FCC catalyst to oil ratio.

[0061] Example 5 is the combined result of two sequential stepsperformed in the captive fluid bed simulating the second and third zoneof the present invention. The presence of a first zone was simulated byusing a lightly coked (0.16 wt % coke) version of the base case catalystin the second zone simulation by coking it with the base vacuum gas oilfeed instead of a secondary light feed due to equipment constraints.Equipment constraints also mandated a reactor temperature of 557° C.Therefore, the results are conservative because the pre-coking with alighter feed and lower reactor temperature would have been expected toincrease the amount of nitrogen removed.

[0062] In the first step of Example 5, the vacuum gas oil feed wascracked at 2.5 catalyst to oil ratio over the lightly coked catalyst.

[0063] The lower nitrogen content liquid product as well as the morehighly coked, but stripped catalyst produced in the first step, werecollected for use in the second step. Nitrogen removal was about 46%.

[0064] Stripping of second zone catalyst would not occur in the actualprocess, but was required to fully material balance the stage-wisesimulation. In the second step, the reactor was charged with a 1:1weight ratio blend of regenerated catalyst with the same coke onregenerated catalyst as the base case (Example 4) and coked, strippedcatalyst collected in step 1, for an overall catalyst to original basevacuum gas oil feed ratio of 4.9. Liquid product from the first stepserved as feed. Overall process yields were obtained by combiningresults of the two steps.

[0065] The results shown in Table 2 illustrate than despite the lowercatalyst to oil ratio, the process of Example 5 resulted in a 2.9 wt %higher 430° F.− (221° C.−) conversion and significant improvement inselectivity as shown by the lower 650° F.+ (343° C.+) bottoms/coke yieldratio. TABLE 2 Wt % 430 F.− 650 F.+ (343° C.) 650 F.+ (343° C.+)Catalyst to (221° C.) Coke Yield, Bottoms Yield, Bottoms/Coke ExampleOil Ratio Conversion wt % wt % Yield Ratio 4 6.1 71.5 7.4 11.7 1.6 5 4.974.4 7.4  8.9 1.2

1. A catalytic cracking process comprising: (a) contacting a firstportion of catalyst with a secondary feed in a first upstream zone, thesecondary feed having a boiling range between about 25° C. and about250° C.; (b) in a first primary feed conversion zone, contacting aprimary feed comprising nitrogen contaminants with the first portion ofcatalyst passed from the first upstream zone, wherein the temperature inthe first primary feed conversion zone is greater than about 450° C.,thereby vaporizing a substantial portion of the primary feed; (c)passing the effluent from the first primary feed conversion zone to asecondary primary feed conversion zone and contacting the effluent fromthe first primary feed conversion zone with a second portion of catalystunder catalytic cracking conditions.
 2. The process according to claim 1wherein the secondary feed further comprises between about 2 and about50 wt % steam based on the total weight of the secondary feed.
 3. Theprocess according to claim 1 wherein the catalyst to secondary feedweight ratio in the first upstream zone is between about 30:1 and about150:1.
 4. The process according to claim 1 wherein the residence time inthe first upstream zone is between about 0.1 and 1 second.
 5. Theprocess according to claim 1 wherein the residence time in the firstprimary feed conversion zone is less than 2 seconds.
 6. The processaccording to claim 1 wherein at least 50 wt. % of the primary feed isvaporized.
 7. The process of claim 1 wherein the effluent of the firstupstream zone has sufficient enthalpy to vaporize at least 80 wt % ofthe FCC primary feed.
 8. The process of claim 1 wherein the effluent ofthe first upstream zone has sufficient enthalpy to vaporize at least 90wt % of the FCC primary feed.
 9. The process according to claim 1wherein the residence time in the second primary feed conversion zone isless than 2 seconds.
 10. The process according to claim 1 furthercomprising contacting a third portion of regenerated catalyst with asecondary FCC feed, the third portion of regenerated catalyst comprisinga catalytic cracking catalyst, the secondary feed comprising steam andhydrocarbons boiling in the range of about 25° C. to about 250° C. andthen passing the third portion of regenerated catalyst and partiallyconverted secondary FCC feed to a third primary feed conversion zone.11. The process according to claim 10 further comprising in the thirdprimary feed conversion zone downstream from the second primary feedconversion zone, contacting the effluent of the second primary feedconversion zone with the third portion of regenerated catalyst whereinthe residence time in the third primary feed conversion zone is betweenabout 0.2 and about 1 second.
 12. The process according to claim 11wherein the weight ratio of the first portion of catalyst to the sum ofthe weights of the second and third portions of catalyst is betweenabout 1:1 and about 1:2 and wherein the weight ratio of the secondportion of catalyst to the third portion of catalyst is between about1:2 and about 1:1.
 13. A catalytic cracking process comprising: (a)contacting a first portion of catalyst with a secondary feed in a firstupstream zone, the secondary hydrocarbon feed having a boiling rangebetween about 25° C. and about 250° C.; (b) in a first primary feedconversion zone, contacting a primary feed comprising nitrogencontaminants with the first portion of catalyst passed from the firstupstream zone, wherein the temperature in the first primary feedconversion zone is sufficient to vaporize at least 80 wt. % of theprimary feed; (c) passing the effluent from the first primary feedconversion zone to a secondary primary feed conversion zone andcontacting the effluent from the first primary feed conversion zone witha second portion of regenerated catalyst under catalytic crackingconditions.
 14. The process according to claim 13 wherein the secondaryfeed further comprises between about 2 and about 50 wt % steam based onthe total weight of the secondary feed.
 15. The process according toclaim 13 wherein the catalyst to secondary feed weight ratio in thefirst upstream zone is between about 30:1 and about 150:1.
 16. Theprocess according to claim 13 wherein the residence time in the firstupstream zone is between about 0.1 and 1 second.
 17. The processaccording to claim 13 wherein the residence time in the first primaryfeed conversion zone is less than 2 seconds.
 18. The process accordingto claim 13 wherein the temperature in the first primary feed conversionzone is at least 450° C.
 19. The process according to claim 13 whereinthe residence time in the second primary feed conversion zone is lessthan 2 seconds.
 20. The process according to claim 13 further comprisingcontacting a third portion of regenerated catalyst with a secondary FCCfeed, the third portion of regenerated catalyst comprising a catalyticcracking catalyst, the secondary feed comprising steam and hydrocarbonsboiling in the range of about 25° C. to about 250° C. and then passingthe third portion of regenerated catalyst and partially convertedsecondary FCC feed to a third primary feed conversion zone.
 21. Theprocess according to claim 20 further comprising in the third primaryfeed conversion zone downstream from the second primary feed conversionzone, contacting the effluent of the second primary feed conversion zonewith the third portion of regenerated catalyst wherein the residencetime in the third primary feed conversion zone is between about 0.2 andabout 1 second.
 22. The process according to claim 21 wherein the weightratio of the first portion of catalyst to the sum of the weights of thesecond and third portions of catalyst is between about 1:1 and about 1:2and wherein the weight ratio of the second portion of catalyst to thethird portion of catalyst is between about 1:2 and about 1:1.